Tunable Dual Emission Research Articles

Dual-modal optical temperature sensing based on Sb3+/Mn2+ co-doped Cs2NaYCl6 double perovskites

Optical temperature sensing based on luminescence intensity ratio shows significant potential in achieving accurate temperature detection. In this work, Sb3+/Mn2+ co-doped Cs2NaYCl6 double perovskites were synthesised via a hydrothermal method. Introducing Sb3+ ions to the host significantly enhances the radiative recombination of self-trapped excitons (STEs), resulting in a broad blue emission. The co-doping of Mn2+ ions to the composition leads to a tunable dual-emission in the spectra, originating from the energy transfer between the STEs and Mn2+ ions. The dependence of the dual-emission on temperature is employed for optical temperature sensing. The maximum relative sensitivity, optimal thermal resolution, and optimal thermal repeatability are determined as 1.40 % K−1, 0.002 K and 99.3% at 250 K, respectively. The results indicate that the synthesised Cs2NaYCl6: Sb3+/Mn2+ double perovskites are promising candidates for high-sensitivity optical thermometers.

Colorimetric detection of Fe2+ and Cr2O72− in environmental water samples based on dual-emitting RhB-embedded Zr-MOFs

Three dye-loaded tunable dual-emission colorimetric fluorescent probes RhB@UiO-66-Ph (R@U-P) were prepared by in-situ encapsulation method under solvothermal conditions. The resonance energy transfer between UiO-66-Ph and RhB made the dual emission of R@U-P easily tunable with the embedded dye content changing. The R@U-P composites achieved emission from purple light to red light, and served as probes to realize comparative detection of Fe3+, Fe2+ and Cr2O72− in water through colorimetric or quenching detection mode. Mechanism study indicates that the resonance energy transfer or electron transfer interactions between R@U-P composites and inorganic ions resulted in the relative changes of the two emission peaks and realized the selective detection of analytes. The preparation and application of R@U-P probes provide a promising strategy for the in-situ encapsulation dye to obtain two dual-emission composites for the comparative detection of Fe3+, Fe2+ and Cr2O72− in water samples.

Tunable dual-emission of Sb3+, Ho3+ Co-doped Cs2NaScCl6 single crystals for light-emitting diodes

Lead-free halide double perovskites are considered as one of the most promising materials in optoelectronic devices, such as solar cells, photodetectors, and light-emitting diodes (LEDs), due to their environmental friendliness and chemical stability. However, the extremely low photoluminescence quantum yield (PLQY) of self-trapped excitons (STEs) emission from lead-free halide double perovskites impedes their applications. Herein, Sb3+ ions were doped into rare-earth-based double perovskite Cs2NaScCl6 single crystals (SCs), resulting in a large enhancement of PLQY from 12.57% to 87.37%. Moreover, by co-doping Sb3+ and Ho3+ into Cs2NaScCl6 SCs, the emission color can be tuned from blue to red, due to an efficient energy transfer from STEs to Ho3+ ions. Finally, the synthesized sample was used in multicolor LED, which exhibited excellent stability and optical properties. This work not only provides a new strategy for improving the optical properties of Cs2NaScCl6 SCs, but also suggests its potential application in multicolor LEDs.

Excitation wavelength-dependent long-afterglow Sb, Mn-doped CsCdCl3 perovskite for anti-counterfeiting applications

Multi-color fluorescent anti-counterfeiting technology possesses a wide range of application prospects. However, there is still a challenge on the development of new single-component multi-color fluorescent materials related to the excitation wavelength. Herein, we report an efficient multi-peak luminescent material, Sb3+, Mn2+ co-doped CsCdCl3, which emission with a long afterglow is related to the excitation wavelength. There are two independent energy transfer channels of Mn2+ under short- and long-wave excitation. Under 357 nm excitation, dual-emission is observed at 506 and 590 nm attributed to the 3P1–1S0 and 4T1-6A1 transitions of [SbCl6]3- and Mn2+ ions, respectively. Under 254 nm excitation, the microcrystals have orange emission. Excitation wavelength-dependent and tunable dual-emission associated with the host self-captured excitons and [SbCl6]3- to Mn2+ energy transfer. The microcrystal's afterglow time at room temperature is 3500 s, which is attributed to the modulation of the trap for Mn2+. These results indicate that the material has potential applications in the field of multicolor fluorescent anti-counterfeiting.

Controlling ESIPT-based AIE effects for designing optical materials with single-component white-light emission

Aggregation-induced emission (AIE) molecules have gained significant importance in various fields such as biological imaging and organic light-emitting diodes. Here, we focused on exploring the process of the induction and control of AIE effects by modifying intramolecular hydrogen bonds. Firstly, inspired by the AIE characteristics of our reported amino-type excited-state intramolecular proton transfer (ESIPT)-based molecules, qualitative and quantitative relationships between the acidity of the amino group and the ESIPT process were investigated. They were successfully revealed through artificial intelligence modeling and quantum chemical calculations. Based on this, eight compounds, (2-(2′-aminophenyl) benzothiazole (1) and its derivatives), were synthesized. Then, their mechanism of structural and optical phenomena (AIE or aggregation-caused quenching (ACQ)) was further verified by quantum chemical calculations and experiments. It has been proved that multistage photochemical reactions could lead to the AIE phenomenon. Finally, the eight compounds were applied to biological imaging and white light material applications, benefiting from tunable dual-emission spectroscopic properties of amino compounds with ESIPT properties. This study provided extensive guidance on developing molecules with AIE properties and opened up new avenues for AIE-based principles, as well as single-component white-light emission optical materials.

Chiral Dual Core Chromophores Based on Binaphthyl Acrylonitrile Motif with Tunable Dual Emission Bands and Anti-counterfeiting.

Small organic molecules which can emit fluorescence with tunable dual emission bands are significant for fundamental research and broad applications. In this work, two binaphthyl based arylacrylonitrile derivatives with pyrene and triphenylamine unit (BiNp-Py and BiNp-TPA) were designed and synthesized, respectively, featuring chiral backbone and dual AIE-active cyanostyrene-linked chromophores. Excellent fluorescence emissions in a range of solution and solid states were observed with high quantum yields, indicative of the solvatochromism and mechanochromism. More interestingly, dual emission bands were found and tunable by the water fraction in THF, and speculatively attributed to the balancing of intramolecular charge transfer (ICT) and locally excited (LE) emission in solution and aggregate states. Furthermore, the potential application in anti-counterfeiting ink was also explored, indicating the very low concentration (5 ppm) for sufficient distinguishable vision and small colour migration (28 nm) for printing on the filter. The present work provides a new strategy to design organic luminescent structure having widely fluorescent emissions in dual states and a valuable reference for the study of chiral optical materials.

Tunable dual color emission from the opposite faces of silicon nanoparticle embedded gel-glass

A luminescent silicon nanoparticle embedded gel-glass, prepared by room temperature hydrolysis and reduction of aminosilane, exhibits intriguing dual photoluminescence (PL) from opposite faces of the glass. The face, which is excited with UV, exhibits excitation energy dependent blue-green emission. As the excitation energy is varied from 350 nm to 450 nm the PL peaks shift from 435 nm to 506 nm. The opposite surface, on the other hand emits nearly excitation independent green light – the PL peak shifts by ∼17 nm as the excitation energy is varied from 350 nm to 450 nm. The luminescent properties provide interesting insights into the light emission mechanism from nanostructured silicon. Spectral filtering by reabsorption and photon reabsorption-reemission in a size distributed nanoparticle system having different optical gaps play a combined role in the observed dual emission. We show that the dual emission can be tuned by simply varying the thickness of the glass. Such dual emission renders the luminescent glass amenable for several applications as a novel solid state display material.

Multicolor emitting luminescent MgO nanocubes for implication in ratiometric optical thermometry

Optical thermometry employing dual emission from two distinct wavelengths for sensing performances has advantages over conventional thermometers due to the self-reference and noninvasive mode of operation. Here, we have demonstrated the synthesis of the multiple colors emitting luminescent MgO nanocubes and explored their temperature-dependent tunable emissions for application in intensity ratio-based optical thermometry. MgO nanocubes are prepared by heating Mg metal ribbons at different temperatures in air ambient. The as-prepared nanocubes exhibit two distinguished photoluminescence emission bands under UV (355 nm) and visible (532 nm) excitations. An excitation and synthesis condition-dependent multicolor emissions are observed in the visible to NIR regions due to the presence of various intermediate defect levels within the band gap of the materials. A temperature-dependent tunable dual emission is realized for different nanocubes, where the two peaks respond to the applied temperature differently, forming an isosbestic point. The difference in the temperature dependency of the two peaks is essential for the fluorescence intensity ratio-based optical thermometry application. The reason for the different responses of the two peaks is explained depending on the presence of the defect levels. From the temperature-dependent intensity ratio variation of MgO nanocubes, the highest sensitivity value of 6.79% K − 1 is achieved, which is very high compared to the various reported ratiometric sensors. The MgO nanocubes demonstrate better stability and reproducibility for application in the 83–513 K wide temperature range.

Multicolor Fluorescent Lead‐MOFs for White‐Light‐Emitting and Anticounterfeiting Applications

AbstractThe synergistic effect of rigid organic framework and soft lattice makes metal‐organic framework (MOF) luminescent materials more widely used. Herein, 2D lead‐MOFs are reported that produce white light through the coregulation of free excitons and self‐trapped excitons. The synthesized BIF‐142‐Cl shows outstanding white‐light emission with the CIE color coordinates of (0.312, 0.335) close to pure white light, the excellent color rendering index (CRI) of 90.4, and the gentle correlation color temperature (CCT) of 5364 K. Meanwhile, the multicolor emission from blue to white light can be adjusted by changing the excitation wavelength. Furthermore, photophysical studies confirm that the strong electronic phonon coupling in the excited state of lead halide polyhedrons is directly responsible for the generation of self‐trapped excitons. This synthetic strategy of introducing tunable dual emission centers not only offers a prospect for the development of solid‐state lighting materials but also widens the path to the fields of anticounterfeiting, display media, and information identification.

Tunable dual-emission in Sb3+, Mn2+ codoped rare-earth based Cs2NaYCl6 nanocrystals and its LEDs applications

Lead-free perovskites are a new type of luminescent material with non-toxic, stability and excellent photoelectric properties, which have great application in the field of photoelectric detection, solar cells, bio-imaging, etc. Here, we reported a new kind of uniform spherical rare-earth based double perovskite Cs 2 NaYCl 6 nanocrystals (NCs) as versatile hosts to accommodate ionic dopants for improving photoelectric properties especially the luminescent properties. In contrast to the low quantum yield of only 5.62%, the luminescent intensity of Cs 2 NaYCl 6 NCs can be impressively enhanced via doping Sb 3+ and Mn 2+ ions in the rare earth-based double perovskite lattices. For the Sb 3+ -doping, the photoluminescence quantum yield (PLQY) increases from 5.62% to 22.48%. On this basis, the luminescence colors can be tuned from blue to white and red via Mn 2+ ions doping and the maximum PLQY can be further improved to 38.66%. Finally, the Sb 3+ , Sb 3+ /Mn 2+ ions doped Cs 2 NaYCl 6 NCs based blue, red and white LEDs were explored, which indicates that these are potential materials in multicolor LEDs applications.

Competing Energy Transfer-Modulated Dual Emission in Mn2+-Doped Cs2NaTbCl6 Rare-Earth Double Perovskites.

A2BIBIIIX6 double perovskites are promising materials due to their outstanding photoelectronic properties and excellent stability in the environment. Herein, we synthesized Mn2+:Cs2NaTbCl6 with dual emission through a solvothermal method for the first time. Mn2+:Cs2NaTbCl6 double perovskites exhibit excellent environmental stability and high photoluminescence quantum yields (PLQYs). The Cs2NaTbCl6 was successfully doped with Mn2+ in two modes: at Mn-feeding concentrations below 1%, Mn2+ first tend to insert into the interstitial void, but if the Mn-feeding concentration exceeds 1%, Mn2+ will further substitute Na+ site of the Cs2NaTbCl6 lattice and thus both two doping modes coexist. After Mn2+ doping, efficient energy transfer from the 5D4 level of Tb3+ ions to the 4T1 level of Mn2+ ions occurs, resulting in tunable dual emission from the Tb3+5D4 → 7FJ=6,5,4,3 transition and Mn2+4T1 → 6A1 transition. Further, LED based on the Mn2+:Cs2NaTbCl6 double perovskites exhibits excellent performance and stability. This work demonstrates a strategy to achieve novel lanthanide-based double perovskites with potential applications in photonics.

Ratiometric fluorescent detection of sulfide ions in Radix Codonopsis and living cells based on PVP-supported gold/copper nanoclusters with tunable dual emission

Herein, a novel fluorometric-sensor with dual-emission system was constructed on the basis of polyvinylpyrrolidone (PVP) and 2-mercaptobenzothiazole (MBT) co-functionalized gold/copper nanoclusters (PVP/MBT-Au@CuNCs) by a facile and eco-friendly one-pot approach. The sensor exhibited ratiometric fluorescence emission (F590 nm/F422 nm) for visual and selective detection of S2− with a sensitive detection limit of 11.9 nM. Besides, fluorescence quenched sensing of S2− was chalked up by a quickly selectivity monitoring time of 30 s, owing to the strongly binding of Cu2S and Au2S by hard-soft-acid-base theory and the destruction of the aggregated structure of PVP/MBT-Au@CuNCs. Furthermore, the platform also provided the portable analysis for visual detection of S2− by capturing the change in fluorescence color with a single dual-emissive ratiometric paper strip. It is worth mentioning that the fluorescent gold-copper nanoclusters showed excellent application activities in the selective detection of S2− in Radix Codonopsis or Tremella samples and recognition of S2− in HeLa cells or macrophages by confocal microscopy fluorescent imaging. Overall, the sensing system paved a new avenue for effectively developing a convenient ratiometric fluorescent sensor platform for evaluating the safety of food with S2− pollution in environment and biological system.

Highly Resolved X‐Ray Imaging Enabled by In(I) Doped Perovskite‐Like Cs3Cu2I5 Single Crystal Scintillator

AbstractLow‐dimensional perovskite halides have shown a great potential as X‐ray detection materials because of efficient exciton emissions originating from strongly spatially localized charge carriers. Nonetheless, most of them have a scintillation yield far below their theoretical limits. Here, it is found that the harvesting efficiency of produced charge carriers can be significantly enhanced via a small amount of In+ doping in these highly localized structures. A bright and sensitive zero‐dimensional Cs3Cu2I5:In+ halide with efficient and tunable dual emission is reported. The radioluminescence emission of Cs3Cu2I5:In+ crystals under X‐ray excitation consists of a self‐trapped exciton emission at 460 nm and an In+‐related emission at 620 nm at room temperature. In+ doping enhances the photoluminescence quantum efficiency (PLQY) of Cs3Cu2I5 from 68.1% to 88.4%. Benefiting from the higher PLQY, Cs3Cu2I5:In+ can achieve an excellent X‐ray detection limit of 96.2 nGyair s−1, and a superior scintillation yield of 53 000 photons per MeV, which is comparable to commercial CsI:Tl single crystals. As a result, a remarkable X‐ray imaging resolution of 18 line pairs mm–1 is demonstrated, which is so far a record resolution for single crystal perovskite‐based flat‐panel detectors. These results highlight the importance of efficient harvesting of carriers (and excitons) in low‐dimensional perovskites for radiation detection applications.

Te4+/Bi3+ Co-Doped Double Perovskites with Tunable Dual-Emission for Contactless Light Sensor, Encrypted Information Transmission and White Light Emitting Diodes

• The energy transfer between Bi 3+ and Te 4+ is realized in Cs 2 ZrCl 6 perovskite. • Bi 3+ /Te 4+ co-doped perovskite can realize color hue evolution from blue to yellow. • High quality WLEDs can be fabricated by Cs 2 ZrCl 6 : Bi 3+ , Te 4+ and UV LED chip. • The phosphor can be exploited in visual light sensor and information transmission. Stable and high-efficiency inorganic lead-free double perovskites have aroused great attention for their application in photoluminescence field. However, most of the double perovskite materials with single dopant cannot realize multi-mode excitation, tunable or full-spectrum emission, which lead to the rare applications in contactless light sensor, encrypted information transmission and white light emitting diodes. Herein, inspired by a traditional methodology of co-doping rare-earth, ns 2 type ions (Bi 3+ and Te 4+ ) co-doped lead-free perovskite Cs 2 ZrCl 6 is proposed and developed. Comparing to the single dopant, Bi 3+ /Te 4+ co-doped perovskites can exhibit high sensitivity to the excitation wavelength and then emit greatly adjustable emission spectra from ∼457 to 577 nm, which corresponds to the color hue evolution from blue to yellow. Meanwhile, the high resonance energy transfer efficiency process from triplet STEs state of Bi 3+ to Te 4+ is also proved by employing the excitation/emission spectra and the transient fluorescence spectrum. Based on the efficient energy transfer process, high quality white light (CIE = (0.330, 0.347), CCT = 5608 K, Ra = 85.1), covering the entire visible region, can be obtained under ultraviolet light excitation. These features guarantee its potential application in contactless light sensor, encrypted information transmission and single-phase white light emitting diodes. The above results show that the methodology of co-doping ns 2 type ions in Cs 2 ZrCl 6 will open up new opportunities to the multifunctional application field.

Dual near infrared emission in Ag2Se quantum dots via Pb doping for broadband mini light-emitting diodes.

Dual emission almost covering the entire NIR-II region with the maximum full width at half maximum of 542 nm was achieved by doping small amounts of Pb ions into Ag2Se quantum dots, which to the best of our knowledge has not been realized for continuous tunable dual NIR emission in Ag-based QDs. The fabricated broadband NIR mini light-emitting diodes based on the Pb-doped Ag2Se QDs exhibit potential applications for highly sensitive and multispectral non-invasive imaging and NIR lighting.

Rational manipulation of lattice strain to tailor the electronic and optical properties of nanostructures

Optoelectronic devices with different energy ranges requires materials with different band gaps, sometimes even within the same device. Structural distortions within the nanostructures produce lattice strains, which can change physical properties. However, the detailed knowledge of lattice strains in nanostructures remains confusing. Here, we rationally design and employ a simple and effective scheme to fabricate strained BiVO4/ZnS nanostructures. Lattice strain originates from lattice distortion caused by the intentional incorporation of metal ions into the inner layer of nanostructures. Experimental findings show that the maximum and minimum band gap energies of BiVO4/ZnS nanostructures are 2.87 and 2.79 eV under the tensile strain, which are increased by 4.4% and 1.4%, respectively, compared with that of the reference sample (2.75 eV). Impressively, BiVO4/ZnS nanostructures exhibit tunable dual emission behavior, and lattice strain significantly changes the electron band structure of the nanostructures. In addition, we identify the composite structure of BiVO4/ZnS nanomaterials and elucidate the mechanistic origin of regulation of the optical and electronic properties by lattice strain in combination with experimental and density functional theory calculations. These results provide a deep understanding of the relationship between lattice strain and optical properties and indicate that strain engineering can be potentially used in the design of nanostructures.

All‐Inorganic Rare‐Earth Halide Double Perovskite Single Crystals with Highly Efficient Photoluminescence

AbstractHalide double perovskites have been regarded as promising alternatives to famous lead halide perovskites in the field of luminescent materials. However, the low‐emission efficiency of pristine ones and the lack of efficient blue emitters remain considerable obstacles for their applications in light‐emitting devices. Here, an air‐stable, all‐inorganic Sc‐based double perovskite Cs2NaScCl6 is reported, which exhibits strong blue emission peaking at 445 nm with an averaged quantum yield of 29.05% (the highest reported value for pristine halide double perovskites). The rare‐earth double perovskite also shows excellent stability against heat and irradiation. Bulk perovskite Cs2NaScCl6 can be an effective host to incorporate Mn2+ ions, yielding interesting tunable dual broadband emission, slightly redshifted blue emission (450 nm) from the host and red emission (635 nm) from Mn2+ d–d transitions. These findings present a new direction toward the design of high‐efficiency, stable, and environmentally friendly perovskite light emitters.

Ratiometric fluorescent sensing of ethanol based on copper nanoclusters with tunable dual emission

Copper nanoclusters (Cu NCs) have attracted a surge of interest in fluorescent sensors as their outstanding physicochemical and optical properties. However, most of the reports have focused on single-signal fluorescent sensors, which are susceptible to background interferences and affect accuracy of the results. Herein, we constructed a facile ratiometric fluorescent sensor for monitoring ethanol based on Cu NCs with tunable dual emission. Polyvinylpyrrolidone (PVP)-modified Cu NCs were simply prepared in water, which exhibit ratiometric dual emission, including a strong green emission at 520 nm and a weak blue emission at 450 nm. The PVP-Cu NCs in water with strong green emission display monodisperse state due to the formation of hydration shell around Cu NCs. In ethanol where the hydration shell is destructed, Cu NCs tend to aggregate and show strong blue emission. This emission shift might attribute to the enhancement of Cu–Cu metallophilic interaction with the aggregation of Cu NCs, which induces the excited-state level increasing. Thus, a ratiometric fluorescent probe for ethanol based on the PVP-Cu NCs is fabricated, which possesses rapid response (<1 min), and realize full-range detection from 0 to 100%. In addition, this ratiometric probe is successfully applied to determine the alcohol strength of alcohol beverages, demonstrating the great potential in practical application.

Tunable dual-emission luminescence from Cu(i)-cluster-based MOFs for multi-stimuli responsive materials

Through filling guest molecules in cages, two Cu(i)-cluster-based MOFs with distinct luminescence at room temperature were obtained. They show multi-stimuli responses to VOCs, temperature and nitro-compounds.

Tunable Dual‐Emission in Monodispersed Sb3+/Mn2+ Codoped Cs2NaInCl6 Perovskite Nanocrystals through an Energy Transfer Process

Double halide perovskites are a class of promising semiconductors applied in photocatalysis, photovoltaic devices, and emitters to replace lead halide perovskites, owing to their nontoxicity and chemical stability. However, most double perovskites always exhibit low photoluminescence quantum efficiency (PLQE) due to the indirect bandgap structure or parity-forbidden transition problem, limiting their further applications. Herein, the self-trapped excitons emission of Cs2 NaInCl6 by Sb-doping, showing a blue emission with high PLQE of 84%, is improved. Further, Sb/Mn codoped Cs2 NaInCl6 nanocrystals are successfully synthesized by the hot-injection method, showing a tunable dual-emission covering the white-light spectrum. The studies of PL properties and dynamics reveal that an energy transfer process can occur between the self-trapped excitons and dopants (Mn2+ ). The work provides a new perspective to design novel lead-free double perovskites for realizing a unique white-light emission.